The use of electronic products of all kinds has increased dramatically throughout society, which has led to a significant increase in the demand for improved components utilized within such products. One facet in the utilization of such electronic products involves the coupling of high frequency signals, e.g., data and/or communications signals, between various signal-bearing components, such as electronic circuit boards.
Some electronic products include a rack or frame into which multiple circuit packs are inserted. Generally, a frame includes a circuit board referred to as a “backplane”, while a circuit pack may include one or more circuit boards. A backplane generally includes multiple connectors soldered to and interconnected by conductive traces. A backplane typically provides little functionality other than electrically interconnecting the circuit boards within the circuit packs. A backplane however may also provide electrical connections external to the frame. When a backplane includes functionality, it may be referred to as a “motherboard”. Such is the case, for example, in a personal computer (PC).
Since back planes are sometimes referred to as motherboards, the circuit packs containing circuit boards that are electrically interconnected using such a motherboard backplane are often referred to as daughter cards. Each daughter card includes one or more circuit boards having electrically conductive traces to electrically interconnect various electrical components in a circuit. Electrical components, such as integrated circuits (ICs), transistors, diodes, capacitors, inductors, resistors, etc., may be packaged with metallic leads that are soldered to conductive traces on a daughter card. A daughter card will typically include a connector, proximate an edge, and soldered to the traces, for electrically coupling to a corresponding connector on the motherboard backplane when inserted into the frame.
One common method of attaching electrical components to a circuit board is to include “through holes”, e.g., holes drilled through the circuit board, and land areas in the traces proximate the holes. Wire leads on the electrical components may then be bent or “formed” or configured for insertion through the holes, and soldered to the land areas once inserted, or “placed.”
Readily available through hole male and female connectors, such as GbXJ, VHDM-HSDJ, VHDM7, Hardmetric (HM), CompactPCI, etc. from manufacturers such as Amphenol, Teradyne, Tyco, etc. are often used for interconnecting two circuit boards. Such connectors are available in various sizes, having various arrays of conductive contact pins. Such arrays of pins are generally held together using a dielectric material, forming the connector. Each pin includes a portion extending from the dielectric material that may be inserted into a through hole in a circuit board. A circuit board for use with a respective connector will have through holes corresponding to the pins of the connector. Conductive traces on the circuit board extend from the land areas corresponding to the pins forming nodes in a circuit.
In production, a circuit board is often placed on a conveyer. As the conveyer moves the board, a solder paste is applied to the board. Through hole electronic components, including connectors, are typically hand placed in the corresponding through holes, the solder paste having been applied. The conveyer then carries the board and connector through an oven that heats the solder paste, soldering the connector to the board. Such a process is generally referred to as “wave soldering”.
Another common method of attaching electrical components to a circuit board is referred to as “surface mounting.” In surface mounting, land areas are also included in the traces, but holes through the circuit board are not necessary. In the case of a surface mount connector, rather than each pin including a portion that may be inserted into a through hole in a circuit board, each pin will include an electrically conductive “foot”. A surface mount connector with conductive feet may be slid over and/or bolted to the edge of a circuit board, the feet corresponding to land areas in the traces on the circuit board. Likewise, in production, surface mount connectors may also be wave soldered.
Irrespective of whether one of these connectors is a through hole or surface mount type, each type suffers from common problems once attached to a circuit board. For example, the pins typically found in these connectors are quite fine, or small. Any deviation in alignment when plugging one connector into another can result in the bending of one or more of these pins. This generally causes either a failure of the product under production test, or worse, a failure of the product in the possession of a user or consumer.
When a pin of a connector is bent, the connector must be removed from the board and a new connector installed. This is can be a time-consuming and difficult process. In the case of a surface mount connector, each of the conductive feet must heated one at a time and bent away from its respective land area to remove the connector. Alternatively, all of the conductive feet must be heated simultaneously to re-flow the solder, allowing the connector to be removed from the board. Typically, a hot air gun is used for such heating. This subjects the board, as well other components adjacent to the connector, to a substantial amount of heat. A heat gun in the hands of an inexperienced repair technician can result in the board being ruined, or the adjacent components being damaged. Even when a heat gun is not used, replacement of a surface mount connector can take a considerable amount of time, and still requires a skilled technician.
In the case of a through hole connector, a heat gun also generally must be used. Through hole connectors typically require even more heat to be applied to a board for removal than surface mount connectors. Again, this makes removal difficult, increasing the chances for an unskilled technician to damage the board or surrounding components. In some cases, with connectors having a large array of pins, it becomes impractical, if not impossible, to simultaneously re-flow the solder on every pin. In such cases, the board must be scrapped.
Another problem inherent in prior art connectors is that the geometric arrangement and/or spacing between pins is not maintained through the connector to the surface of a respective circuit board. For example, pins in such connectors are generally used in pairs, a pair of pins carrying either a single ended or differential data and/or communications signal. Deviation in the geometric arrangement and/or spacing of between pins when used as a pair generally results in impedance variation with a change in frequency, thereby degrading the electrical performance of the connector and/or limiting the usable frequency range of the connector. Further, since these pins are arranged in an array, and pairs of pins are generally in close proximity to other pairs of pins, there can be, and often is electromagnetic interaction between pairs and/or pins. Such interaction is typically referred to as “crosstalk”. Ideally, these pins would be consistently spaced throughout, and the connectors would provide some sort of shielding of the pairs to prevent crosstalk. Such connectors provide no shielding, nor is consistent spacing possible. Therefore, there is a need in the prior art to improve upon the connectivity between circuit board and respective motherboards. There is specifically a need to address the problems with such connectors when used with boards handling high-speed data and other communications signals.
One type of connectors used for electrically coupling an electrical component to a circuit board is an elastomeric connector. Generally, an elastomeric connector comprises a body constructed of an elastic polymer material having opposing first and second faces and a plurality of fine conductors that are passed from the first to the second faces. An elastomeric connector may be positioned between land areas on a circuit board and conductive leads on the component, aligning the leads with the land areas. Pressure is then applied to the connector to compress the elastic polymer, providing electrical connection from the land areas on a circuit board on one face through the conductors to leads of the component on the other face. One example of the use of such an elastomeric connector is in electrically coupling a liquid crystal display (LCD) screen to a circuit board in a calculator. However, signals between an LCD screen and a circuit board are low frequency digital signals not high frequency data/communications signals. Therefore, there is little concern for the geometric arrangement of the components or shielding. Thus, elastomeric connectors are essentially often just parallel data and/or power lines.
There have been other uses of elastomeric materials, such as in test fixtures to electrically contact integrated circuit chips in production testing, to couple a ribbon cable to a circuit board, or in coupling a pin grid array to a circuit board. However, again the elastomeric connectors when so used are generally parallel data and/or power lines. Yet another use of an elastomeric material has been in the form of a seal in a connector to thereby extend the shielding provided by an outer conductor in a data cable. Therefore, elastomeric connectors, to date, are essentially for power transfer or simple low frequency digital signal transfer or shielding. Therefore, such connectors have not been particularly suited to the transfer of high frequency signals, e.g., data and/or communications signals in a connector assembly between two circuit boards.
It is desirable to address drawbacks in the prior art in providing high frequency data and/or communications connections between electrical circuit boards.
Furthermore, it is desirable to maintain the geometric arrangement and alignment of conductors in a connector.
Additionally, it is desirable to improve the replacement and serviceability of a high-speed data connector assembly.
It is further desirable to provide multiple such connections in a compact arrangement, such as an array, that are shielded.
These objectives and other objectives will become more readily apparent from the summary of invention and detailed description of embodiments of the invention set forth herein below.